The present invention relates to a method of controlling a cylinder apparatus which is driven by pneumatic pressure.
In a cylinder apparatus, as a method of preventing a piston from colliding against the inner wall of a cylinder at the end point position of the cylinder at high speed by decelerating the moving piston halfway through the stroke, a method disclosed in Japanese Patent Application No. 4-16335 which was previously filed by the present applicant is known.
In this method, as shown in the flow chart in FIG. 1, compressed air of a first high pressure is supplied to one chamber of a cylinder, which is divided into two chambers by a piston, and air is exhausted from the other chamber, thereby moving the piston in the extending direction of the cylinder. When the piston passes a position in front of a sensor attached at the middle position of the cylinder, air of a second high pressure lower than the first high pressure is supplied into the other chamber, thereby decreasing the moving speed of the piston.
However, in the above-mentioned prior art, since the sensor for detecting the deceleration start position is fixed at a specific position of the cylinder, the following problems are posed.
More specifically, in a normal cylinder apparatus, as a result of continuous movement of the piston, the sliding resistance of the piston gradually changes due to a temperature rise caused by the friction of a seal portion of the cylinder or due to spread of an oil in the entire cylinder. For this reason, when the sensor is fixed at a specific position, and the deceleration start point is fixed in position all the time, even if the piston can smoothly reach the end point in an initial state, the piston may stop before it reaches the end point, or may reach the end point before it is sufficiently decelerated, with an elapse of time. When the piston stops halfway, an object to be conveyed by the piston cannot be conveyed to a target position. Conversely, when the piston reaches the end position before it is sufficiently decelerated, the piston collides against the inner wall of the cylinder, and is damaged. In order to solve these problems, the sensor for detecting the deceleration start position can be moved with respect to the cylinder to adjust the deceleration start position of the piston. However, such an adjustment is very troublesome.